Whitepaper
Modeling of Tapered Anechoic Chambers
This paper presents a hybrid numerical method for simulating electromagnetic fields within tapered anechoic chambers, particularly focusing on improving accuracy at lower frequencies (below 500 MHz) where traditional ray tracing methods like SBR struggle. The approach combines Finite Element Method (FEM) modeling of the chamber throat – including the source antenna - with Floquet mode analysis to represent absorber arrays as virtual surfaces and subsequent application of the Shooting and Bouncing Ray (SBR) method for the remainder of the chamber. FEM calculates equivalent currents at the throat interface, which serve as sources for SBR. The authors validated this technique against full-wave simulations using ANSYS HFSS for a 54m chamber (42m tapered, 12m rectangular) with pyramidal absorbers on all walls and observed good agreement in field distribution, including longitudinal ripples and transverse amplitude tapering from 100MHz to 300 MHz.